Highlights A transportable spectrometer performed similarly to benchtop spectrometers to predict forage quality. Absorption bands in the second and third overtone regions were used to predict forage quality with ample accuracy. A low-cost handheld spectrometer was useful for routine screening of forage for nitrogen content. Abstract . Assessing the nutritional composition of animal feed and forage materials is important to achieve high animal productivity and wellness. Precision nutrition programs that use NIR technology can determine the nutritional composition of feed and forage quickly and simply, generating actionable information such as total nitrogen (N), acid detergent fiber (ADF), neutral detergent fiber (NDF), and acid detergent lignin (ADL) contents, as well as in vitro dry matter digestibility (IVDMD). Recent advances in optics and microelectronics have allowed for the development of handheld spectrometers that are portable, robust, and user-friendly. However, are the handheld units accurate enough to predict nutritional content of animal feed? In this study, the performance of two handheld NIR spectrometers to predict the nutritional content of forage based on N, ADF, NDF, ADL, and IVDMD was evaluated by comparing them to two benchtop NIR spectrometers often used in feed and forage analysis. The forage samples comprised switchgrass (Panicum virgatum L), big bluestem (Andropogon gerardi), and Indiangrass (Sorghastrum nutans). The first handheld spectrometer covers 780-2500 nm with a spectral interval (??) of 1 nm, while the second handheld spectrometer is a palm-sized smartphone spectrometer covering 900-1700 nm with ?? = 4 nm. The benchtop spectrometers both cover 400-2500 nm with ?? = 2 nm. Forage samples were scanned on each spectrometer and divided into calibration (n = 143) and validation (n = 35) sets. Partial least squares (PLS) regression was used to calibrate all spectrometers using mean-centered spectral data that had been preprocessed using Savitzky-Golay first derivative (SG1) or second derivative (SG2) algorithm with 9-63 smoothing points. Results showed that PLS models that best predicted N using the benchtop spectrometers had lower standard error of prediction (SEP = 1.24-1.28 g kg-1) and higher ratio of prediction to deviation (RPD = 3.66-3.78) compared to the models developed based on spectra collected from the handheld spectrometers (SEP = 1.46-1.78 g kg-1; RPD = 2.39-2.84). ADF, NDF, and ADL were variable and generally poorly predicted using spectra from the benchtop spectrometers (SEP = 10.02-33.19 g kg-1;RPD = 1.71-2.24), and even more so using the handheld spectrometers (SEP = 10.63-32.57 g kg-1;RPD = 1.64-2.47). Predicting IVDMD was similar for both sets of benchtop (SEP = 40.00-41.73 g kg-1; RPD = 2.24-2.34) and handheld (SEP = 34.46-40.84 g kg-1; RPD = 2.29-2.72) spectrometers. These results show that the handheld devices can be used for screening of forage samples based on N, which is a closely monitored component in animal feed and forage, as well as IVDMD, an important forage quality index. Keywords: Forage, Portable spectrometer, Spectroscopy, Screenin, Ruminant nutrition.

Breeding to improve biomass production of switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman) for conversion to bioenergy began in 1992. The purpose of this study was (i) to develop a platform for uniform regional testing of cultivars and experimental populations for these species, and (ii) to estimate the gains made by breeding during 1992 to 2012. A total of 25 switchgrass populations and 16 big bluestem populations were planted in uniform regional trials at 13 locations in 2012 and 2014. The reference region was USDA Hardiness Zones 3 through 6 in the humid temperate United States. Significant progress toward increased biomass yield was made in big bluestem and within upland-ecotype populations, lowland-ecotype populations, and hybrid-derived populations of switchgrass. Four mechanisms of increasing biomass yield were documented: (i) increased biomass yield per se, (ii) later flowering to extend the growing season, (iii) combined later flowering from the lowland ecotype with survivorship of the upland ecotype in hybrid-derived populations, and (iv) increased survivorship of late-flowering lowland populations in hardiness zones that represent an expansion of their natural adaption zone. Switchgrass exhibited all four mechanisms in one or more improved populations, whereas improved populations of big bluestem were likely influenced by two of the four mechanisms. The uniform testing program was successful at documenting increases in biomass yield, identifying the mechanisms for increased yield, and determining adaptation characteristics and limitations of improved populations.

Red imported fire ants (Solenopsis invicta) have caused damage to agricultural, economic, and wildlife resources since their accidental introduction. Previous studies have suggested that red imported fire ant (RIFA) mound densities are positively correlated to habitats maintained through disturbance. Prescribed burning and disking are two techniques commonly used to disturb portions of the landscape to maintain early successional habitats for northern bobwhite (Colinus virginianus). We tested the hypothesis that prescribed burning and disking would increase RIFA mound densities. This study was conducted in Refugio County, Texas in the Texas Coastal Prairie on Loamy Prairie range sites. Red imported fire ant mound densities were different between years (F = 5.05, df = 2, P = 0.0148). However, burning and disking had no impact (F = 0.22, df = 2, P = 0.8044) on RIFA mound densities. Initially high RIFA mound densities in our study area coupled with the territoriality of predominantly monogyne (single-queen) colonies may have limited increases in RIFA mound density in response to treatments on these study sites.

Switchgrass (Panicum virgatum) is a C4 perennial grass and is the model herbaceous perennial bioenergy feedstock. Although it is indigenous to North American grasslands east of the Rocky Mountains and has been planted for forage and conservation purposes for more than 75 years, there is concern that switchgrass grown as a biofuel crop could become invasive. Our objective is to report on the invasion of C4 and C3 grasses into the stands of two switchgrass cultivars following 10 years of management for biomass energy under different N and harvest management regimes in eastern Nebraska. Switchgrass stands were invaded by big bluestem (Andropogon gerardii), smooth bromegrass (Bromus inermis), and other grasses during the 10 years. The greatest invasion by grasses occurred in plots to which 0 N had been applied and with harvests at anthesis. In general, less grass encroachment occurred in plots receiving at least 60 kg of N ha−1 or in plots harvested after frost. There were differences among cultivars with Cave-in-Rock being more resistant to invasion than Trailblazer. There was no observable evidence of switchgrass from this study invading into border areas or adjacent fields after 10 years of management for biomass energy. Results indicate that switchgrass is more likely to be invaded by other grasses than to encroach into native prairies or perennial grasslands seeded on marginally productive cropland in the western Corn Belt of the USA.

Biofuels and bio-based products can be produced from a wide variety of herbaceous feedstocks. To supply enough biomass to meet the needs of a new bio-based economy, a suite of dedicated biomass species must be developed to accommodate a range of growing environments throughout the USA. Researchers from the US Department of Agriculture’s Agricultural Research Service (USDA-ARS) and collaborators associated with the USDA Regional Biomass Research Centers have made major progress in understanding the genetics of switchgrass, sorghum, and other grass species and have begun to use this knowledge to develop new cultivars with high yields and appropriate traits for efficient conversion to bio-based products. Plant geneticists and breeders have discovered genes that reduce recalcitrance for biochemical conversion to ethanol and drop-in fuels. Progress has also been made in finding genes that improve production under biotic and abiotic stress from diseases, pests, and climatic variations.

Dedicated energy crops and crop residues will meet herbaceous feedstock demands for the new bioeconomy in the Central and Eastern USA. Perennial warm-season grasses and corn stover are well-suited to the eastern half of the USA and provide opportunities for expanding agricultural operations in the region. A suite of warm-season grasses and associated management practices have been developed by researchers from the Agricultural Research Service of the US Department of Agriculture (USDA) and collaborators associated with USDA Regional Biomass Research Centers. Second generation biofuel feedstocks provide an opportunity to increase the production of transportation fuels from recently fixed plant carbon rather than from fossil fuels. Although there is no “one-size-fits-all” bioenergy feedstock, crop residues like corn ( Zea mays L.) stover are the most readily available bioenergy feedstocks. However, on marginally productive cropland, perennial grasses provide a feedstock supply while enhancing ecosystem services. Twenty-five years of research has demonstrated that perennial grasses like switchgrass ( Panicum virgatum L.) are profitable and environmentally sustainable on marginally productive cropland in the western Corn Belt and Southeastern USA.

The Regional Feedstock Partnership is a collaborative effort between the Sun Grant Initiative (through Land Grant Universities), the US Department of Energy, and the US Department of Agriculture. One segment of this partnership is the field-scale evaluation of switchgrass (Panicum virgatum L.) in diverse sites across the USA. Switchgrass was planted (11.2 kg PLS ha−1) in replicated plots in New York, Oklahoma, South Dakota, and Virginia in 2008 and in Iowa in 2009. Adapted switchgrass cultivars were selected for each location and baseline soil samples collected before planting. Nitrogen fertilizer (0, 56, and 112 kg N ha−1) was applied each spring beginning the year after planting, and switchgrass was harvested once annually after senescence. Establishment, management, and harvest operations were completed using field-scale equipment. Switchgrass production ranged from 2 to 11.5 Mg ha−1 across locations and years. Yields were lowest the first year after establishment. Switchgrass responded positively to N in 6 of 19 location/year combinations and there was one location/year combination (NY in Year 2) where a significant negative response was noted. Initial soil N levels were lowest in SD and VA (significant N response) and highest at the other three locations (no N response). Although N rate affected some measures of biomass quality (N and hemicellulose), location and year had greater overall effects on all quality parameters evaluated. These results demonstrate the importance of local field-scale research and of proper N management in order to reduce unnecessary expense and potential environmental impacts of switchgrass grown for bioenergy.

ABSTRACT Pollination bags for making controlled crosses between switchgrass ( Panicum virgatum L.) plants were made from a polyester micromesh fabric with a mesh size of 41 µm, which is smaller than the mean reported 43 µm diameter of switchgrass pollen. When used in paired‐plant crosses between switchgrass plants, the mean amount of seed produced per plant was about 1 g, or approximately 800 seeds, which was significantly greater than the 10 to 250 seeds produced previously in paired‐plant crosses of switchgrass using paper pollination bags. The four‐ to tenfold increase in seed produced per cross enables the progeny of the crosses to be evaluated in larger numbers in genetic studies and in replicated space‐transplanted or seeded sward evaluation trials. The micromesh pollination bags cost about $15 each because of fabric costs but could be reused for 10 or more pollination seasons at an annual cost per cross of about $1.50 or less.

'Liberty' (Reg. No. CV-271, PI 669371) switchgrass (Panicum virgatum L.) is a lowland-type cultivar that is adapted to USDA plant hardiness zones (HZ) 4, 5, and 6 in the U.S. Great Plains and Midwest, east of 100 degrees W. longitude. It was developed for use as a perennial biomass energy crop and is the first high-yielding biomass-type lowland cultivar adapted to this region. It can produce greater biomass yields than upland-or forage-type switchgrass cultivars developed previously for use in the region, and it has equivalent winter survival. Liberty has significantly greater winter survival in its adaptation region than previously released lowland switchgrass cultivars such as 'Kanlow' and 'Alamo' that frequently have substantial winter damage and stand loss north of 40 degrees N latitude in the U.S. Great Plains and Midwest.

'Newell' (Reg. No. CV-275, PI 671851) smooth bromegrass (Bromus inermis Leyss.) is a steppe or southern type cultivar that is primarily adapted in the United States to areas north of 40 degrees N and east of 100 degrees W that have 500 mm or more annual precipitation or in areas that have similar climatic conditions because of elevation or latitude. It was developed to replace 'Lincoln', which is the most widely used smooth bromegrass cultivar in the region, by improving its forage digestibility. Newell bromegrass was developed by four generations of population improvement breeding for in vitro dry matter digestibility (IVDMD) and forage yield using Lincoln as the base population. In regional small plot trials, Newell produced forage with greater IVDMD than Lincoln and equivalent or greater forage yields. In a replicated grazing trial in eastern Nebraska, beef yearlings grazing Newell for a 3-yr period produced significantly greater average daily gains and beef production per hectare than yearlings grazing Lincoln bromegrass.

ABSTRACTBiomass composition of switchgrass (Panicum virgatum L.) can affect its utilization by ruminants and its conversion to liquid fuels in a biorefinery. The objective of this study was to evaluate the effects of six generations of divergent breeding for forage in vitro dry matter digestibility (IVDMD) on switchgrass biomass composition, forage quality traits, and ethanol yield. Initially there was one cycle of selection for both low (C‐1) and high IVDMD (C1 = cv. Trailblazer), followed by four additional breeding cycles for high IVDMD. In cycles 4 and 5, winter survival was included as a selection criterion because of decreased winter survival of the C3 population. The experimental populations that were produced by these breeding generations and nine half‐sib families from cycle 5 were evaluated for two post‐establishment years at the research station in eastern Nebraska, where all the breeding work was conducted. The six breeding generations resulted in significant differences among the populations for all the 28 cell wall and non‐cell‐wall composition variables measured, forage quality, and ethanol yield traits measured except for total biomass C, cell wall concentration, soluble glucose, and etherified ferulates. These traits included all cell wall and nonstructural carbohydrates. Breeding for the heritable complex trait IVDMD affected a large number of plant biomass characteristics and also adversely affected plant biomass yield and winter survival.

ABSTRACTCrop science is a highly integrative science employing expertise from multiple disciplines to broaden our understanding of agronomic, turf, and forage crops. A major goal of crop science is to ensure an adequate and sustainable production of food, feed, fuel, and fiber for our world's growing population. The Crop Science Society of America (CSSA) identified key Grand Challenges which, when addressed, will provide the tools, technologies, and solutions required to meet these challenges. The Grand Challenges are: (i) Crop adaptation to climate change: Increase the speed with which agriculture can adapt to climate change by using crop science to address abiotic stresses such as drought and heat. (ii) Resistance to biotic stresses: Increase durability of resistance to biotic stresses that threaten yield and quality of major crops. (iii) Management for resource limited systems: Create novel crop cultivars and management approaches designed for problem soils and low‐input farming to increase economic prosperity for farmers and overcome world hunger. (iv) Crop management systems: Create novel crop management systems that are resilient in the face of changes in climate and rural demographics. (v) Biofuels: Develop sustainable biofuel feedstock cropping systems that require minimal land area, optimize production, and improve the environment. (vi) Bioresources: Genotyping the major crop germplasm collections to facilitate identification of gene treasures for breeding and genetics research and deployment of superior genes into adapted germplasm around the globe. These challenges are intended to be dynamic and change as societal needs evolve. Available funding and national prioritization will determine the rate that they will be addressed.

The effect of switchgrass (Panicum virgatum L.) seed quality tests on field establishment has been addressed inadequately. Our objective was to evaluate the ability of seed quality tests to predict field establishment. Standard Association of Official Seed Analysts (AOSA) tests are based on the percentage of seeds in a seedlot that germinate under standard laboratory conditions, whereas the seedlot establishment tests (SETs) are based on the number of seeds that emerge per gram of seed using different germination or stress test conditions. The SET was determined using six laboratory tests and the results validated in three replicated field trials. Treatments were: (i) AOSA pure live seed (PLS) test assuming 858 seeds g−1; (ii) AOSA test with no prechill; (iii) AOSA test with prechill; (iv) heat stressed at 50°C for 12 h; (v) emergence from 4 cm of sand; and (vi) heat stressed plus emergence from 2 cm of sand. Data from noncontrol tests were on a SET per‐gram basis. Field establishment differed by the seed quality test on which the seeding rate was based. The best predictor of field establishment was emergence from 4 cm of sand, which had an establishment index (ratio of field‐emerged seeds to seeds planted) that was 3.5 times greater than the PLS method and 36% greater than no prechill. Stands on which planting rates were based on SET that included stress tests were better predictors of field establishment than the standard PLS method. Switchgrass seeding rates based on SET are recommended to reduce the risk of failure during stand establishment.

Information on temporal and spatial variation in switchgrass ( Panicum virgatum L.) biomass composition as it affects ethanol yield (L Mg −1 ) at a biorefinery and ethanol production (L ha −1 ) at the field‐scale has previously not been available. Switchgrass biomass samples were collected from a regional, on‐farm trial and biomass composition was determined using newly developed near‐infrared reflectance spectroscopy (NIRS) prediction equations and theoretical ethanol yield (100% conversion efficiency) was calculated. Total hexose (cell wall polysaccharides and soluble sugars) concentration ranged from 342 to 398 g kg −1 while pentose (arabinose and xylose) concentration ranged from 216 to 245 g kg −1 across fields. Theoretical ethanol yield varied significantly by year and field, with 5 yr means ranging from 381 to 430 L Mg −1 . Total theoretical ethanol production ranged from 1749 to 3691 L ha −1 across fields. Variability (coefficient of variation) within established switchgrass fields ranged from 1 to 4% for theoretical ethanol yield (L Mg −1 ) and 14 to 38% for theoretical ethanol production (L ha −1 ). Most fields showed a lack of spatial consistency across harvest years for theoretical ethanol yield or total theoretical ethanol production. Switchgrass biomass composition from farmer fields can be expected to have significant annual and field‐to‐field variation in a production region, and this variation will significantly affect ethanol or other liquid fuel yields per ton or hectare. Cellulosic biorefineries will need to consider this potential variation in biofuel yields when developing their business plans.

Four switchgrass cultivars (Trailblazer, Cave-in-Rock, Summer, and Kanlow) were grown at the University of Nebraska Agricultural Research and Development Center. Each cultivar was hand-harvested to a 10 cm stubble height on 3 July 2002. Five Panicum maximum samples were collected on 4 February 2005 in the municipality of Xinguara, Para, Brazil. Two additional P. maximum samples were collected from Para. Two Brachiaria humidicola [Urochloa humidicola], two B. decumbens [Urochloa decumbens] and one B. brizantha [Urochloa brizantha] samples were also collected. Saponins were extracted from these plant materials. The total saponin content in the switchgrass samples was consistent across the different varieties ranging from a low of 0.108 % for the Cave-in-Rock variety to a high of 0.124% for the Summer variety. In comparing switchgrass cultivars, the concentrations of dichotomin, protodioscin, and saponin B in the Summer Trailblazer and Cave-in-Rock cultivars are very similar with dichotomin as the major saponin. Among the four switchgrass cultivars analyzed, Kanlow was the most distinct in its saponin profile. The differences in saponins across cultivars may be explained by differences in ecotype. Summer, Trailblazer, and Cave-In-Rock are upland ecotypes and had similar saponin profiles. Kanlow, a lowland ecotype, had a dissimilar saponin profile to the upland ecotypes. The two B. decumbens samples had saponin levels of 1.55% and 1.15%. The B. brizantha sample had a total saponin level of 0.628%. These Brachiaria samples are from pastures where photosensitization occurred in sheep and had high levels of total protodioscin and saponins when compared to the Panicum samples. One B. humidicola sample, had a low level of protodioscin while one did not have any measurable protodioscin, dichotomin, or saponin B. Both of these samples are from pastures where photosensitization occured in horses.

The capacity of perennial grasses to affect change in soil properties is well documented but information on switchgrass (Panicum virgatum L.) managed for bioenergy is limited. An on-farm study (10 fields) in North Dakota, South Dakota, and Nebraska was sampled before switchgrass establishment and after 5 years to determine changes in soil bulk density (SBD), pH, soil phosphorus (P), and equivalent mass soil organic carbon (SOC). Changes in SBD were largely constrained to near-surface depths (0–0.05 m). SBD increased (0–0.05 m) at the Nebraska locations (mean=0.16 Mg m−3), while most South Dakota and North Dakota locations showed declines in SBD (mean=−0.18 Mg m−3; range=−0.42–0.07 Mg m−3). Soil pH change was significant at five of the 10 locations at near surface depths (0–0.05 m), but absolute changes were modest (range=−0.67–0.44 pH units). Available P declined at all sites where it was measured (North Dakota and South Dakota locations). When summed across the surface 0.3 m depth, annual decreases in available P averaged 1.5 kg P ha−1 yr−1 (range=0.5–2.8 kg P ha−1 yr−1). Averaged across locations, equivalent mass SOC increased by 0.5 and 2.4 Mg C ha−1 yr−1 for the 2500 and 10 000 Mg ha−1 soil masses, respectively. Results from this study underscore the contribution of switchgrass to affect soil property changes, though considerable variation in soil properties exists within and across locations.

'Homestead' (Reg No CV-255, PI 655522) Canada wildrye (Elymus canadensis L) was developed cooperatively by USDA-ARS and the University of Nebraska and was released in 2008 for use in the Great Plains and the Midwest USA, a region for which no adapted cultivars were previously available It was developed by means of the Ecotype Selection Breeding System from a collection made in a remnant prairie in Eastern Nebraska USA Homestead, which was tested as NE3, is adapted to Plant Adaptation Region (PAR) 251-5 (Temperate Prairie Parkland-Plant Hardiness Zone 5), which is its origin, and in which it has been evaluated in both space-transplanted and sward trials This region is equivalent to USDA Plant Hardiness Zone 5 of the tallgrass-prairie ecoregion of the Midwest, USA When grown in its area of adaptation, it produces more forage than the previously available, unadapted cultivar of the species and its forage has higher in vitro dry matter digestibility than another adapted experimental strain to which it was compared in sward forage yield trials Its primary use will be as a native cool-season grass component of conservation, roadside, and grassland seeding mixtures